U.S. stock index futures edged lower on Tuesday as conflict in the Middle East entered its fifth day, dampening global investor confidence ahead of the Federal Reserve's upcoming policy meeting.

US stock futures fell with investors on edge as Israel and Iran continued to trade strikes against a backdrop of shifting US trade policy and stubborn interest rates.

Markets are concerned about Iran's frequent threats to blockade the Strait of Hormuz, just as the US heads into peak summer demand season.

S&P 500 futures are down 0.6%. Dow Jones Industrial Average futures are dipping 0.7%. Nasdaq 100 futures are retreating 0.6%. On Monday, the Dow Jones Industrial Average rose 317 points, or 0.75%, to 42,

Gold futures pared gains after rising close to a fresh record earlier in the session. Futures were down 0.5% at $3,433.90 a troy ounce, after opening near the record high of $3,509.90/oz. The precious metal rallied on Friday as rising Middle East tensions fuelled safe-haven demand,

U.S. ultra-low sulfur diesel futures hit the highest level since February, outpacing gains in oil and gasoline as analysts warned that diesel supply is the most exposed to the conflict in the Middle East.

U.S. futures for the S&P 500 were down 0.6% and futures for the Dow Jones Industrial Average declined 0.7%. Changes in futures do not necessarily predict movements after the opening bell.

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